1. Field of the Invention
The present invention relates to an apparatus and a method for manufacturing a laminated substrate (panel) by laminating two substrates.
2. Description of the Related Art
Recently, with flat panel displays such as liquid crystal displays (LCDs) becoming larger and thinner, the demand for a reduction in the cost of manufacturing such displays is increasing. To meet such a demand, an apparatus for laminating two substrates is also required for application in such enlargement while improving productivity.
A liquid crystal panel is manufactured in the following manner. First, an array substrate (TFT substrate), in which a plurality of TFTs (thin film transistors) are formed in a matrix, and a color filter substrate (CF substrate), in which color filters (red, green, blue) and a light shielding film are formed, are arranged facing each other with an extremely narrow gap (approximately a few micrometers) in between. Liquid crystal is filled in the gap between the two substrates. The light shielding film is used to obtain high contrast or to shield the TFTs and prevent the occurrence of light leakage current. The TFT substrate and the CF substrate are laminated with a sealing material (adhesive) that contains, for example, a thermosetting resin.
In the conventional method for manufacturing the liquid crystal panel, a liquid crystal-dropping process is performed when filling the liquid crystal between two glass substrates. More specifically, a frame of the sealing material is formed on one side of the TFT substrate along the edges of the substrate. A certain amount of liquid crystal is dropped onto a region defined in the frame of the sealing material. Subsequently, the TFT substrate and the CF substrate are laminated in a vacuum environment to seal the liquid crystal between the substrates.
After filling the liquid crystal, the two substrates are laminated by pressurizing the two substrates using a laminating device or a pressing apparatus. The pressing apparatus includes an upper holding plate and a lower holding plate arranged facing each other in a processing chamber. The pressing apparatus moves the two holding plates toward each other with the holding plates parallel to each other to keep the gap between the two substrates even.
A conventional pressing apparatus will now be described with reference to FIGS. 1 to 3. In a processing chamber, lower holding members 2 are movable on a table 1 in upward and downward directions. A pressing plate 3 is arranged above the lower holding members 2 and is movable in upward and downward directions.
Robot hands 4a, 4b convey an upper substrate W1 and a lower substrate W2 into the processing chamber and a laminated substrate (panel) W3 out of the processing chamber. Shutters 5, normally positioned outside the processing chamber, enter the processing chamber when the upper substrate W1 is conveyed into processing chamber. The shutters 5 aid in attracting the upper substrate W1 to the pressing plate 3.
The conveying operation of the substrates W1 and W2 will now be discussed. First, the robot hand 4a attracting and holding an upper surface of the upper substrate W1 enters the processing chamber. The shutters 5 then close and enter the processing chamber, as shown in FIG. 2.
As shown in FIG. 3, the robot hand 4a is then lowered. This places the peripheral portion of the substrate W1 on the shutters 5. Further, the central portion of the substrate W1 is attracted to an upper holding member (not shown). The robot hand 4a then releases the substrate W1 and moves out of the processing chamber. When moving out of the processing chamber, the robot hand 4a conveys the substrate W3, which was laminated in the previous cycle and which is supported on the lower holding members 2, out of the processing chamber.
The upper holding member is then raised and the substrate W1 is attracted to the pressing plate 3. The substrate W2 held by the robot hand 4b is conveyed into the processing chamber and attracted to the table 1.
After the robot hand 4b is moved out of the processing chamber, the processing chamber is tightly sealed. Then, the pressing plate 3 is lowered to press and laminate the substrates W1 and W2 with the table 1.
Japanese Patent Publication No. 2002-229044 describes a conventional example of the substrate laminating apparatus.
In the prior art, the means for holding the substrates W1 and W2 on the pressing plate 3 and the table 1 is either a vacuum chuck (vacuum attraction means) or an electrostatic chuck (electrostatic attraction means).
When laminating the substrates W1, W2 in a depressurized processing chamber, the vacuum chuck stops functioning to hold the substrates. Thus, the substrates W1 and W2 are electrostatically held. More specifically, voltage is applied to electrodes arranged on the table 1 and the pressing plate 3 and to an electrically conductive film formed on the substrate. This generates Coulomb force between the substrate and the electrode and electrostatically attracts the substrate.